DNS服务器介绍

DNS是计算机域名系统(Domain Name System 或Domain Name Service) 的缩写，它是由域名解析器和域名服务器组成的。域名服务器是指保存有该网络中所有主机的域名和对应IP地址，并具有将域名转换为IP地址功能的服务器。

[root@localhost ~]# cat /etc/resolv.conf 
nameserver 192.168.xxx.xxx
#search localdomain
[root@localhost ~]# 

[root@localhost ~]# nslookup 127.0.0.1 | grep Server
Server:         192.168.xxx.xxx
[root@localhost ~]# 

root@localhost ~]# dig 
 
; <<>> DiG 9.3.6-P1-RedHat-9.3.6-16.P1.el5 <<>>
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 36888
;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 3
 
;; QUESTION SECTION:
;.                              IN      NS
 
;; ANSWER SECTION:
.                       86163   IN      NS      m.root-servers.net.
.                       86163   IN      NS      a.root-servers.net.
.                       86163   IN      NS      j.root-servers.net.
.                       86163   IN      NS      l.root-servers.net.
.                       86163   IN      NS      e.root-servers.net.
.                       86163   IN      NS      d.root-servers.net.
.                       86163   IN      NS      k.root-servers.net.
.                       86163   IN      NS      f.root-servers.net.
.                       86163   IN      NS      h.root-servers.net.
.                       86163   IN      NS      c.root-servers.net.
.                       86163   IN      NS      g.root-servers.net.
.                       86163   IN      NS      b.root-servers.net.
.                       86163   IN      NS      i.root-servers.net.
 
;; ADDITIONAL SECTION:
a.root-servers.net.     3599    IN      A       112.4.20.71
b.root-servers.net.     86163   IN      A       192.228.79.201
i.root-servers.net.     86173   IN      A       192.36.148.17
 
;; Query time: 8 msec
;; SERVER: 192.168.xxx.xxx#53(192.168.xxx.xxx)
;; WHEN: Sat Apr 16 07:34:37 2016
;; MSG SIZE  rcvd: 289
 
[root@localhost ~]# dig | grep SERVER: | awk -F# '{ print $1 }' | awk -F: '{ print $2 }'
 192.168.xxx.xxx